1. Field of the Invention
The present invention relates to a suspension system, and more particularly to a front suspension system for an electric wheelchair.
2. Related Prior Art
A suspension system is generally provided with a shock absorbing device and links which are used to reduce the bounce or impact to the vehicle caused by a bumpy road, so as to keep the passengers comfortable.
FIG. 1 shows that an electric wheelchair C1 moves on a bearing surface G, to the front end of a frame C11 of the electric wheelchair C1 are secured two front wheel retainers C12, each of which is provided with a front shock absorber C13, and to the rear end of the frame C11 are secured two rear wheel retainers C14, and each being provided with a rear shock absorber C15. The front and rear shock absorber C13, C15 can slow down the up and down motion of the frame C11, so as to improve riding comfort.
Each of the front wheel retainers C12 consists of a first section C121 and a second section C122 coupled to the first section C121, the first section C121 is disposed at an angle of approximately 30 degrees with respect to the bearing surface G, and the second section C122 is parallel to the bearing surface G. The first section C121 has one end pivoted to the frame C11 and another end coupled to one end of the second section C122 which has another end provided with a front wheel C16. Each of the front shock absorbers C13 has one end pivoted to a corresponding one of the first section C121. When the front wheels C16 of the electric wheelchair C1 encounters a raised obstacle, the front wheel retainers C12 will pivot upward to make the front wheels C16 climb over the obstacle.
Therefore, the climbing capability of the electric wheelchair C1 is determined by pivoting capability of the front wheel retainers C12. The higher the pivoting of the front wheel retainers C12, the bigger the climbing capability of the electric wheelchair C1, and the greater the shock absorbing performance against bumpy road will be.
However, the end of the front wheel retainers C12 pivoted to the frame C11 is also restricted by the front shock absorber C13 (for easy explanation, only one set of front wheel and its relative components are described), the pivoting angle of the front wheel retainer C12 is closely linked with the structure arrangement of the front wheel retainer C12 and the location of the front shock absorber C13. Since the front wheel retainer C12 is pivoted to the first section C121 of the front wheel retainer C12, and the first section C121 is located adjacent to the front shock absorber C13 and inclined towards the bearing surface G, the initial position of the pivoting of the front wheel retainer C12 is the angle position of the first section C121, and the finish position of the pivoting is the position of the front shock absorber C13, namely, the pivoting angle of the front wheel retainer C12 is restricted between the front shock absorber C13 and the first section C121. The arrangement of the first section C121 being inclined towards and located adjacent to the front shock absorber C13 substantially narrows the pivoting capability of the front wheel retainer C12, and as a result, the climbing capability of the electric wheelchair C1 climbing over the obstacles is limited.
Referring then to FIG. 2, another conventional electric wheelchair C2 is provided with a front wheel retainer C22 and a rear wheel retainer C23 which are fixed to the front and rear ends of a frame C21 of the wheelchair C2, respectively, for mounting of a front wheel C24 and a rear wheel C25, respectively. The front suspension system of the frame C2 includes the front wheel retainer C22 and a spring C26 which is perpendicularly disposed on the front wheel retainer C22.
With the elasticity of the spring C26, the front wheel retainer C22 can move up and down along with the front wheel C24 to absorb the bounce caused by bumpy road. When the wheelchair moves on a flat and smooth or a little bumpy road, the direction in which the front wheel retainer C22 presses the spring C26 is the same as the direction that the spring C26 are compressed, the spring C26 is in the best condition for damping and shock absorbing.
When moving on a very bumpy road, the front wheel C24 bounces up and down and causes movement of the front wheel retainer C22, the front wheel retainer C22 will press against the spring C26 in an inclined manner. Therefore, the front wheel retainer C22 presses laterally against the spring C26, namely, the direction in which the press force is applied by the front wheel retainer C22 is different from the direction that the spring C26 is compressed, which will cause bending of the spring C26, and the damping effect is adversely affected. Besides, the more bumpy the road is, the greater the upward pressing force applied to the front wheel retainer C22 will be. When the upward pressing force applied to the front wheel retainer C22 is big, and the elastic force of the spring C26 is the only force to counteract the upward pressing force, once the elastic force of the spring C26 is not big enough to counteract the upward pressing force, the frame C2 of the wheelchair will tip backward, and as a result, the wheelchair won't be able to move safely on the bumpy road.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.